Centrifugal chuck device

ABSTRACT

Centrifugal force responsive means for holding a tool in the bore of a spindle, in which the tool is carried by a tool holder insertable into and removable from the spindle bore, the tool holder having an inner end provided with a cavity, and a chuck being disposed in the spindle bore and having spring fingers, the ends of which engage in the cavity of the tool holder to initially hold the tool holder in the spindle, and the gripping action of the chuck fingers is increased by centrifugal force.

United States Patent Kosmowski [54] CENTRIFUGAL CHUCK DEVICE [72]Inventor: Wojclech B. Kosmowski, Covina, Calif.

[73] Assignee: Advanced Controls Corporation, Pico Rivera, Calif.

22 Filed: Nov. 9, 1970 [2!] Appl. No.: 87,992

[52] [1.5. CI ..90/l1 A, 279/1 B, 279/1 C, 279/46, 279/103, 279/104 [51]Int. Cl ..B23c 5/26, B23b 31/04 [58] Field of Search ..90/11 A; 279/1 B,1 C, 15 G, 279/102, 23, 96, 104,103, 41, 89, 90, 46

[56] References Cited UNITED STATES PATENTS 3,168,322 2/1965 Dziedzic..90/ll A X June 27, 1972 2,356,245 8/1944 Johnston ..279/iC PrimaryExaminer-Gil Weidenfeld Attorney-Newton H. Lee, Jr.

[57] ABSTRACT Centrifugal force responsive means for holding a tool inthe bore of a spindle, in which the tool is carried by a tool holderinsertable into and removable from the spindle bore, the tool holderhaving an inner end provided with a cavity, and a chuck being disposedin the spindle bore and having spring fingers, the ends of which engagein the cavity of the tool holder to initially hold the tool holder inthe spindle, and the gripping action of the chuck fingers is increasedby centrifugal force.

11 Claims, 4 Drawing Figures PATENTEDJum m2 256 INVENTOR. WOJC'L/E'CH B,KOJMOWJIU BYWKJ CENTRIFUGAL CHUCK DEVICE BACKGROUND OF THE INVENTION Inthe manufacture of various articles requiring the use of a machine toolin which a tool is held by a chuck, it frequently becomes necessary thatthe tool be changed. Such change requires that the machine tool be shutdown for the period of time necessary to effect the change. If themachine is of the multi-spindle type, say a multiple spindle drill pressin which all of the drills in the spindles are changed periodically, thelapsed time when the machine is shut down may be very extensive and,thus, very expensive in respect of the unit cost of the useful workperformed by the machine.

In order to avoid excessive shut down time, an approach to the problemhas involved the utilization of multiple drills in turrets which may beshifted through a series of successive stations so that the shutdowntime is reduced to the period of time required to change stations,but this leads to substantial initial cost of the machinery.

In addition to the foregoing, alignment and depth of penetration withinacceptable tolerances are serious problems in the efiicient use ofmachine tools such as drill presses employed in the drilling of holes inprecision devices, particularly devices in which a number of holes aredrilled simultaneously. Indeed, the combined cost of shut down timeduring drill change and establishment of precise alignment of the drillsmay become substantially intolerable, so that there has long been a needfor means which enable the rapid change of tools in a drill presswhereby the tools may not only be rapidly changed, but may also beprecisely aligned coaxially with the spindle and precisely positioned toeffect the desired penetration.

In the past, efforts have been made to accomplish the rapid and accuratechange of drills in drill presses by the provision of variouscentrifugally operated chucks or collets. For example, it is known toprovide a gripping device within the spindle of high speed dental drillsby longitudinally slotting a tubular member and forming its ends so thatsegments of the slotted member form levers, weighted ends of which arerocked by centrifugal force about a fulcrum'which engages the inside ofthe'spindle to effect a grip on the shank of a dental burr by grippingends of the levers. In addition, it has been proposed that a tool suchas a drill be initially combined with a separate member constitutingacollet which is insertable into a bore of a spindle, the collet havingintegral fingers which are expanded by centrifugal force into engagementwith the spindle wall.

Such prior devices inherently experience problems in respect of toolalignment, balance, and positioning, and more particularly, thecentrifugally operable collets must be employed in large numbers, due tothe fact that the collet is initially combined with the drill or tool,thus, requiring precision manufacture of a large number of collets.

SUMMARY OF THE INVENTION The present invention provides a chuck orgripping device of the centrifugally operated type adapted to becombined with the spindle of a rotary machine tool and adapted toautomatically engage a holder for a tool which is inserted into thespindle.

More particularly, the invention provides a means whereby the tool maybe combined with a holder and kept in readiness for installation in thespindle upon removal of a similar holder from the spindle. The toolholder and the chuck or gripping device are so constructed that theaccuracy of positioning and concentricity of the tool as well as properbalance are assured. In addition, the chuck or gripping device comprisesa plurality of integrated flexible arms, end portions of which engage ina socket or recess in the inner end of the tool holder, wherebycentrifugal force caused by rotation of the spindle automatically causesthe fingers to grip the tool holder and cause corresponding rotation ofthe latter. With such a combination, the tool holder is a comparativelysimple device which can be inexpensively made in quantities which willenable the maintenance of a suitable number of tool holders and tools inreadiness for installation into the machine tool spindle; whereas, themore complex chuck or gripping device remains in place in the spindle.

This invention possesses many other advantages, and has other purposeswhich may be made more clearly apparent from a consideration of a formin which it may be embodied. This form is shown in the drawingsaccompanying and forming part of the present specification. It will nowbe described in detail, for the purpose of illustrating the generalprinciples of the invention; but it is to be understood that suchdetailed description is not to be taken in a limiting sense, since thescope of the invention is best defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation showing amachine tool spindle and a tool holder and tool to be associated withthe spindle;

FIG. 2 is an enlarged view, partly in vertical section and partly inelevation, showing the tool holder and tool engaged with the chuck inthe spindle;

FIG. 3 is a detailed view in side elevation and on an enlarged scale,showing the centrifugal chuck; and

FIG. 4 is an end elevation of the chuck of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT As seen in the drawings, aspindle S isprovided as a portion of a machine tool M adapted to receivea tool holder H which carries a tool T in the form of a drill. Themachine tool M, without requiring further illustration, may be of thewell known type in which the spindle S essentially constitutes a portionof a rotor of a high speed electrical motor, whereby the spindle isadapted to be rotated a number of thousands of revolutions per minute,as is the case of well known high speed precision drill presses, whichmay comprise a plurality of spindles S, each driven by its own motor andcombined in a drill press so that the plurality of the drills or tools Twill be moved simultaneously into engagement with a part to be drilled.It is in connection with the operation of such high speed precisiondrills that the problem of frequent tool change of a number of tools andthe requirement of precise alignment and balance are most pronounced,since substantial down time of the machine and skilled labor in changingthe tools have heretofore been involved.

Referring to FIG. 2, the spindle S will be seen to comprise acylindrical bore 10 temtinating in an inner wall 11 which is normal tothe axis of the spindle. Within the spindle bore 10 is a gripping deviceor chuck C which engages the inner end of the tool holder H to retainthe latter in the bore 10 during use of the tool T.

Referring more particularly to the chuck C, it will be seen that it isof unitary construction and includes an inner annular end section orportion 12 sized to be press fit into the bore 10 and into abuttingengagement with the wall 11. The end section 12 is drilled and tapped asat 13 to enable installation and removal of the chuck C by use of athreaded tool (not shown), as is obvious. Extending longitudinally fromand integral with .the end section 12 is a plurality ofcircumferentially spaced resilient finger portions 14 which are spacedapart by elongated slots 15 extending longitudinally from the free endsof the fingers 14 substantially to the flexible juncture of the fingers14 with the end section 12. Each of the fingers has in spaced relationto the end section 12 a radially enlarged weight portion 16, thediametrical distance across the weight portions being less than thediameter of the bore 10. At the free ends of the fingers 14, the fingerseach have a gripping portion 17 extending axially from a wall 18 whichis normal to the axis of the chuck. The gripping portions 17 flareslightly from the wall 18 to a juncture 19 with a chamfer 20. In eifect,the gripping portions 17 combine to form a short frustum of a long cone.

Tool holder H, at its inner end, has an annular cavity defined by a wall21 which is also a frustum of a long cone generally corresponding tothat provided by the end portions 17 of the chuck C, so that when theholder H is inserted into the spindle bore 10, as seen in FIG. 2, theend portions 17 engage with the wall 21 of the holder H, the dimensionsbeing such that fingers 14 are initially at least slightly stressedinwardly to establish initial gripping contact of the portions 17 of thecollet with the wall 21 of the tool holder H. In this connection, thecharnfer 20 facilitates inward deflection of the fingers 14 as the ends17 of the latter are forced into the end of the tool holder H uponinsertion of the tool holder into the spindle S.

The tool holder H comprises an elongated cylindrical body 22 having acentral bore 23 adapted to receive the shank 24 of the tool of drill T.At its other end, the body 22 is provided with means for gripping thetool shank 24 and centralizing it. This means comprises a taperedbushing 25 engageable in a tapered seat 26 and adapted to be forcedinwardly to grip the tool shank 24 and centralize the latter by a nut 27which is threaded as at 28 into the end of the body 22. Other means maybe utilized to retain the tool T in the holder H, but preferably suchmeans also should centralize the tool T with respect to the holder body22.

In order to facilitate inserting of the holder H into the bore of thespindle S and into engagement with the chuck C, as well as to facilitateremoval of the holder H from the spindle S, the body 22 ata locationexternal of the spindle S is provided with means engageable by asuitable changing tool or automatic apparatus. Thus, the body 22 in theillustrated embodiment has an annular groove 29 providing a firstshoulder 30 facing outwardly with respect to the spindle S and a secondshoulder 31 facing inwardly with respect to the spindle S, theseshoulders enabling the application of an endwise force to the holderbody 22 by too] changing apparatus as referred to above.

While the specific details of the illustrative embodiment of theinvention have been described, it will be appreciated that changes oralterations may be resorted to. The essence of the invention resides inthe fact that the chuck C is installed in and remains in the spindle Sunless damage or wear requires replacement, and provides flexiblefingers 14 having sufficient mass in the weighted portions 16 to producesubstantial centrifugal force, in response to high speed spindlerotation, to cause the gripping portions 17 of the fingers 14 to tightlyengage within the end cavity of the tool holder H, so that rotation iseffectively transmitted to the tool T. However, the holder H may bereadily removed from the spindle S and be replaced by a similar holderhaving a new tool T. Since inward movement of the holder H into thespindle bore 10 is limited by abutting engagement of the holder H withthe walls 18, the groove 29 is positively located to facilitatemanipulation of the holder H by automatic machinery, if desired. Suchprecise positioning of the tool holder H also allows the tool T to beprecisely located with respect to the holder H so that the penetrationof the drill into a work piece will be predetermined.

[ claim:

1. A chuck device comprising: a rotatable spindle having a bore coaxialwith the axis of rotation, a chuck in said bore having a plurality ofcircumferentially spaced elongated and resilient fingers, said fingersincluding means being responsive to centrifugal force to urge the freeends of said fingers outwardly, a holder in said bore, said holder andsaid fingers having coengaged portions confining said fingers againstoutward movement upon rotation of said spindle, and said holder havingmeans for supporting a member to be rotated.

2. A chuck device as defined in claim 1, wherein said chuck comprises anend section from which said fingers extend and with which said fingersare integral, said fingers being relatively thin and flexible at thejuncture with said end section, and said fingers having weight portionsadjacent the free ends of said fingers and responsive to centrifugalforce to urge the free ends 0 said fingers outwardly, said portions ofsaid fingers coengageable with said holder being at the free ends ofsaid fingers.

3. A chuck device as defined in claim 1, wherein said chuck comprises anend section from which said fingers extend and with which said fingersare integral, said fingers being relatively thin and flexible at thejuncture with said end section, and said fingers having weight portionsadjacent the free ends of said fingers and responsive to centrifugalforce to urge the free ends of said fingers outwardly, said portions ofsaid fingers coengageable with said holder being at the free ends ofsaid fingers, said weight portions having end faces engageable by saidholder.

4. A chuck device as defined in claim 1, wherein said chuck comprises anend section from which said fingers extend and with which said fingersare integral, said fingers being relatively thin and flexible at thejuncture with said end section, and said fingers having weight portionsadjacent the free ends of said fingers and responsive to centrifugalforce to urge the free ends of said fingers outwardly, said portions ofsaid fingers coengageable with said holder being at the free ends ofsaid fingers, said holder having a cavity in an end thereof bordered bya wall cooperative with said coengaged portions of said fingers to gripsaid holder responsive to centrifugal force.

5. A chuck device as defined in claim 1, wherein said chuck comprises anend section from which said fingers extend and with which said fingersare integral, said fingers being relatively thin and flexible at thejuncture with said end section, and said fingers having weight portionsadjacent the free ends of said fingers and responsive to centrifugalforce to urge the free ends of said fingers outwardly, said portions ofsaid fingers coengageable with said holder being at the free ends ofsaid fingers, said portions at the free ends of said fingerscoengageable with said holder being initially flexed inwardly toinitially retain said holder connected to said chuck.

6. A chuck device as defined in claim 1, wherein said holder is providedwith means external of said spindle for accomodating a tool forinserting said holder into said spindle and pulling said holder fromsaid spindle.

7. A chuck device as defined in claim 6, wherein said means foraccomodating a tool comprises oppositely facing shoulders on saidholder.

8. A chuck device as defined in claim 1, wherein said chuck is press fitin said bore, and includes means connectable to a pulling tool to removesaid chuck from said bore.

9. A chuck device as defined in claim 1, wherein said holder has acentral opening and means for centralizing and holding a shank in saidopening.

10. A chuck device comprising: a rotatable spindle having a bore coaxialwith the axis of rotation, chuck means in said bore including aplurality of circumferentially spaced elongated and resilient fingers,said fingers including means being responsive to centrifugal force tourge the free ends of said fingers outwardly, and said free ends each ofsaid fingers having means engageable in a cavity of a holder in the boreof said spindle for retaining the holder in the bore and for rotatingsaid holder in response to rotation of said spindle.

11. A chuck device as defined in claim 10, wherein said chuck comprisesan end section from which said fingers extend and with which saidfingers are integral, said fingers being relatively thin and flexible atthe juncture with said end sec tion, and said fingers having weightportions adjacent the free ends of said fingers and responsive tocentrifugal force to urge the free ends of said fingers outwardly.

1. A chuck device comprising: a rotatable spindle having a bore coaxialwith the axis of rotation, a chuck in said bore having a plurality ofcircumferentially spaced elongated and resilient fingers, said fingersincluding means being responsive to centrifugal force to urge the freeends of said fingers outwardly, a holder in said bore, said holder andsaid fingers having coengaged portions confining said fingers againstoutward movement upon rotation of said spindle, and said holder havingmeans for supporting a member to be rotated.
 2. A chuck device asdefined in claim 1, wherein said chuck comprises an end section fromwhich said fingers extend and with which said fingers are integral, saidfingers being relatively thin and flexible at the juncture with said endsection, and said fingers having weight portions adjacent the free endsof said fingers and responsive to centrifugal force to urge the freeends of said fingers outwardly, said portions of said fingerscoengageable with said holder being at the free ends of said fingers. 3.A chuck device as defined in claim 1, wherein said chuck comprises anend section from which said fingers extend and with which said fingersare integral, said fingers being relatively thin and flexible at thejuncture with said end section, and said fingers having weight portionsadjacent the free ends of said fingers and responsive to centrifugalforce to urge the free ends of said fingers outwardly, said portions ofsaid fingers coengageable with said holder being at the free ends ofsaid fingers, said weight portions having end faces engageable by saidholder.
 4. A chuck device as defined in claim 1, wherein said chuckcomprises an end section from which said fingers extend and with whichsaid fingers are integral, said fingers being relatively thin andflexible at the juncture with said end section, and said fingers havingweight portions adjacent the free ends of said fingers and responsive tocentrifugal force to urge the free ends of said fingers outwardly, saidportions of said fingers coengageable with said holder being at the freeends of said fingers, said holder having a cavity in an end thereofbordered by a wall cooperative with said coengaged portions of saidfingers to grip said holder responsive to centrifugal force.
 5. A chuckdevice as defined in claim 1, wherein said chuck comprises an endsection from which said fingers extend and with which said fingers areintegral, said fingers being relatively thin and flexible at thejuncture with said end section, and said fingers having weight portionsadjacent the free ends of said fingers and responsive to centrifugalforce to urge the free ends of said fingers outwardly, said portions ofsaid fingers coengageable with said holder being at the free ends ofsaid fingers, said portions at the free ends of said fingerscoengageable with said holder being initially flexed inwardly toinitially retain said holder connected to said chuck.
 6. A chuck deviceas defined in claim 1, wherein said holder is provided with meansexternal of said spindle for accomodating a tool for inserting saidholder into said spindle and pulling said holder from said spindle.
 7. Achuck device as defined in claim 6, wherein said means for accomodatinga tool comprises oppositely facing shoulders on said holder.
 8. A chuckdevice as defined in claim 1, wherein said chuck is press fit in saidbore, and includes means connectable to a pulling tool to remove saidchuck from said bore.
 9. A chuck device as defined in claim 1, whereinsaid holder has a central opening and means for ceNtralizing and holdinga shank in said opening.
 10. A chuck device comprising: a rotatablespindle having a bore coaxial with the axis of rotation, chuck means insaid bore including a plurality of circumferentially spaced elongatedand resilient fingers, said fingers including means being responsive tocentrifugal force to urge the free ends of said fingers outwardly, andsaid free ends each of said fingers having means engageable in a cavityof a holder in the bore of said spindle for retaining the holder in thebore and for rotating said holder in response to rotation of saidspindle.
 11. A chuck device as defined in claim 10, wherein said chuckcomprises an end section from which said fingers extend and with whichsaid fingers are integral, said fingers being relatively thin andflexible at the juncture with said end section, and said fingers havingweight portions adjacent the free ends of said fingers and responsive tocentrifugal force to urge the free ends of said fingers outwardly.